The present invention relates generally to internal combustion engines for automotive vehicles, and more specifically, to an automotive vehicle having a starter/alternator coupled between the engine and transmission and to a method for engaging and disengaging the engine from the transmission.
Automotive vehicles with internal combustion engines are typically equipped with both a starter motor and alternator positioned in different locations on the engine. In recent years, a combined alternator and starter motor has been proposed. To date the cost and complexity of combining these systems into one device has prevented it from being used in a production embodiment.
With new interest in hybrid electric vehicles, the starter-alternator can assume other functions such as stopping and restarting the engine to save fuel during idle and deceleration, aiding the engine during heavy accelerations and capturing energy during decelerations.
Known systems typically have a rotor mounted directly to the crankshaft of the engine and a stator sandwiched between the engine block and the bell housing of the transmission. During startup of the vehicle, the starter/alternator functions as a starter rotating the crankshaft of the engine while the cylinders are fired. After the engine is started, the starter/alternator is used as a generator to maintain the electrical system of the vehicle.
One drawback to such systems is that the rotor remains fixedly attached to the crankshaft. When the engine is not operating, it may be desirable to provide the transmission with power supplied by the starter-alternator. However, to do this the crankshaft of the unoperating engine is rotated. This is inefficient because an increased amount of power must be provided.
It would therefore be desirable to disengage the engine from the starter/alternator rotor to reduce the inefficiency of turning the crankshaft of the engine when operation of the engine is not required.
It is therefore one object of the invention to increase the efficiency of the starter/alternator during operation of the vehicle under the control of the starter/alternator.
In one aspect of the invention, a starter/alternator system for an automotive vehicle with an internal combustion engine has a crankshaft coupled to pistons and a flywheel coupled to the crankshaft. The vehicle also has a transmission having an input shaft. A starter/alternator has a rotor and a stator. The rotor is fixedly coupled to the input shaft. A clutch selectively couples the input shaft and the crankshaft.
The rotor has a rotor carrier and a rotor coil. One feature of the invention is that the rotor carrier has a radially extending portion and an annular portion spaced from the input shaft. The annular portion has an inner surface and outer surface wherein the rotor coil is fixedly coupled to the outer surface.
In another aspect of the invention, the starter/alternator may be used to inertia balance the engine. That is, the starter/alternator may be modulated to provide a torque to reduce the effective inertia of the starter/alternator system so that the engine does not have an increased inertial load due to the starter/alternator system.
One advantage of the invention is that axial movement of the rotor with respect to the stator due to magnetic forces is reduced.
Other objects and features of the present invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and appended claims.